The corpus luteum (CL) plays a major role in the primate reproductive process. The hormones produced by the CL are necessary for the successful implantation of the ovum in the uterus and hence a successful pregnancy. Little is known about the mechanisms involved in the control of this "endocrine" gland. Recent evidence indicates that several gonadal peptides one of which is oxytocin (OT) may be involved in luteal development. Using the baboon as an experimental model the objectives of this study are a) to evaluate the effects of prostaglandin F2a on CL hormone production, b) to examine the effect of OT and hCG on PGF, 6- ketoprostaglandin F1a and 5-HETE production. These effects will be examined using an in vitro dispersed cell preparation, in short term incubations (3 hr), long term (24-48 hr) culture and in vivo using local infusion techniques, c) to examine the exact site in the steroidogenic pathway where OT may have its effect, d) to determine if the action of OT is receptor mediated, using CL membrane preparations and autoradiography, e) to measure PGF 2a receptors using CL membrane preparation and f) to determine if ovarian OT is biologically active using an in vitro bioassay. The hormones in the media from the in vitro studies and in blood (femoral ovarian veins, contralateral to the CL and ipsilateral vein) will be assayed by radioimmunoassay. Enzyme assays will be used to determine the site of action of OT in corpus luteum steroidogenesis. The data obtained will provide a more integrated picture of the mechanisms controlling the primate CL which may permit new approaches to fertility regulation as well as a better understanding of therapy of early reproductive failures or difficulties due to ovulatory or corpus luteum dysfunction. Similarly it may enable new approaches to the treatment of menstrual dysfunction.